In general, an LCD device using thin film transistors (TFTs) as switching elements implements colors through operations of thin film transistors (TFTs) and liquid crystal cells that control a transmission rate of white color emitted from a backlight and through additive mixture of three colors transmitted through color filters including R, G and B.
Herein, as for the color filters, which apparently looks like a general element plate, flat panel matrixes are formed on a glass substrate and R, G and B filter layers with excellent light transmittance are formed therebetween.
A shape, dimension and color arrangement of the color filters differ according to the purpose of an LCD. In other words, the arrangement of color filters includes a strip arrangement, a mosaic arrangement and a delta arrangement.
Actually, in the color filters, R, G and B pixels are connected with TFTs in a one-to-one manner on a liquid crystal panel. As the requirements for the color filters, first, color filters are to have high coloration density, high light transmittance, second, they are not to have a color change or discoloration with respect to a backlight, and third, they are to be chemically stable and harmless to a liquid crystal material.
A general color filter structure and types of its fabricating methods will be described. Although not shown, in general, a black matrix is formed on a glass substrate or the like, and R, G and B color filter layers are formed to partially overlap with the black matrixes between the black matrixes. A passivation film is formed to protect the color filter layers, on which a common electrode is formed as a transparent electrode.
The black matrixes are generally positioned between the R, G and B patterns of the color filter in order to shield a portion where a pixel electrode is not formed and reverse tilted domains.
The black matrix also serves to prevent an increase in a leakage current by blocking direct light irradiation on the TFT used as a switching element.
The color filter is fabricated by a dye method and a pigment method depending on an organic filter, and the fabrication can be classified into a dyeing method, a distribution method, an electrodeposition method and printing method. The fabrication method of the color filter will be described as follows.
First, the printing method is to fabricate color filters by printing R, G and B ink on a substrate through several printing methods. A typical printing method includes a screen printing, an offset printing, etc. Since the printing method is simple, it can be used for mass-production, and a material with a high heat resistance or light resistance can be used. But the printing method has disadvantages in that a pinhole due to an air bubble, spreading of color density, discoloration can be easily generated, and perpendicularity at an edge of a pattern can be degraded due to a leakage of ink during printing process.
The electrodeposition method is to form a colorant layer by depositing coloring matter on an electrode. According to this method, a polymer resin and coloration pigment are dissolved or dispersed in an electrolyte solvent to deposit the pigment on a surface of a transparent electrode connected to both sides and dried at a high temperature. However, the electrodeposition method has such problems that if a specific resistance of the transparent electrode is high, spreading occurs, and the transparent electrode can be damaged by a component, which causes a chemical reaction with the transparent electrode, contained in the electrolyte solvent. In particular, the transparent electrode has a low chemical resistance and thus severely influenced to be damaged, so after the electrodeposition, color density and light transmittance are degraded.
In case of the LCD using the TFTs, the pigment spreading method is generally used for fabricating the color filters. Primary components of the color filter pigment fabricated by the pigment spreading method include a photopolymerization type photosensitive composition such as a photopolymerization initiator, monomer, binder, etc., and an organic pigment implementing colors.
The process of fabricating a color filter substrate which is required to have low reflection characteristics generally includes forming black matrixes using a chrome/chromeoxide (Cr/CrOx), forming color filters by the pigment spreading method, and forming a common electrode.
The related art process of fabricating the color filters of the LCD using the pigment spreading method will be described with reference to FIGS. 1a to 1e. 
FIGS. 1a to 1e show sequential sectional views of a process for fabricating color filters of the related art LCD.
With reference to FIG. 1a, like a TFT array substrate, first, a substrate 10 is cleansed, and then Cr/CrOx used as a material of the black matrix is deposited on the substrate 10.
Next, the Cr/CrOx layer is selectively patterned through an exposure and development process using photolithography to form a plurality of black matrixes. In this case, formation of the black matrix 11 is directly related to an aperture ratio, so its designing must be prudent, and because CrOx is etched by a general Cr etching solution, the Cr/CrOx is simultaneously etched.
Subsequently, with reference to FIG. 1b, a red pigment is deposited entirely on the substrate including the plurality of black matrixes 11, and selectively patterned by the exposure and development process using the photolithography to form a red color filter layer 13 on a portion of the substrate 10.
And then, with reference to FIG. 1c, a green color pigment is deposited entirely on the substrate including the red color filter layer 13 and then selectively patterned by the same process as in FIG. 1b, namely, by the exposure and development process using the photolithography to form a green color filter layer 15 on a portion of the substrate 10.
Thereafter, with reference to FIG. 1d, a blue color pigment is deposited entirely on the substrate 10 including the green color filter layer 15, and then selectively patterned by the same process as in FIG. 1b, namely, by the exposure and development process using the photolithography to form a blue color filter layer 17 on a portion of the substrate 10.
And then, with reference to FIG. 1e, after the color filter layer formation process is completed, an overcoat layer 19 is deposited entirely on the substrate to planarize the surface thereof.
As mentioned above, the related art color filter fabrication method of the LCD has the following problems. That is, when the color filters are fabricated by the pigment spreading method, waste of pigment is severe. That is, in order to form the red color filter layer, the red color pigment is deposited entirely on the substrate but remain on the necessary portion (e.g., ⅓ portion) while the pigment deposited on the other portions (e.g., ⅔ portions) are removed, resulting in a waste of much pigment.
In particular, a cost for the device, process and material for forming the color pigment during the color filter fabrication is high in the fabrication cost of the color filters, so the overall color filter fabrication cost increases.